path: root/src/imports/threed/shaderprogram.cpp

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#include "shaderprogram.h"
#include "shaderprogram_p.h"
#include "qglabstracteffect.h"
#include <QtOpenGL/qglshaderprogram.h>
#include <QWeakPointer>

#include <QDeclarativeEngine>
#include <QDeclarativeContext>
#include <QFile>

#include "qglscenenode.h"
/*!
    \qmlclass ShaderProgram ShaderProgram
    \brief The ShaderProgram item is derivative class of the more general Effect class in QML/3d.
    Whereas the Effect class provides support for standard effects under OpenGL, the ShaderProgramEffect supports effects based on custom shader programs for the GPU.
    \since 4.8
    \ingroup qt3d::qml3d
    \inherits Effect

    The ShaderProgram class provides Qml/3d users with the ability to use a  QGLShaderProgram within the
    logical context of the normal \l Effect class provided by Qml/3d.

    If the system does not support shaders, then ShaderProgram will
    behave the same as \l Effect, with support for simple lit
    materials only.

    \section1 Attributes

    ShaderProgram provides a standard set of 8 vertex attributes that
    can be provided via the geometry \l Mesh:

    \table
    \header \o Shader Variable \o Mesh Attribute \o Purpose
    \row \o \c qt_Vertex \o QGL::Position
         \o The primary position of the vertex.
    \row \o \c qt_Normal \o QGL::Normal
         \o The normal at each vertex, for lit material effects.
    \row \o \c qt_Color \o QGL::Color
         \o The color at each vertex, for per-vertex color effects.
    \row \o \c qt_MultiTexCoord0 \o QGL::TextureCoord0
         \o The texture co-ordinate at each vertex for texture unit 0.
    \row \o \c qt_MultiTexCoord1 \o QGL::TextureCoord1
         \o Secondary texture co-ordinate at each vertex.
    \row \o \c qt_MultiTexCoord2 \o QGL::TextureCoord2
         \o Tertiary texture co-ordinate at each vertex.
    \row \o \c qt_Custom0 \o QGL::CustomVertex0
         \o First custom vertex attribute that can be used for any
            user-defined purpose.
    \row \o \c qt_Custom1 \o QGL::CustomVertex1
         \o Second custom vertex attribute that can be used for any
            user-defined purpose.
    \endtable

    These attributes are used in the vertexShader, as in the following
    example of a simple texture shader:

    \code
    attribute highp vec4 qt_Vertex;
    attribute highp vec4 qt_MultiTexCoord0;
    uniform mediump mat4 qt_ModelViewProjectionMatrix;
    varying highp vec4 texCoord;

    void main(void)
    {
        gl_Position = qt_ModelViewProjectionMatrix * qt_Vertex;
        texCoord = qt_MultiTexCoord0;
    }
    \endcode

    \section1 Standard uniform variables

    ShaderProgram provides a standard set of uniform variables for
    common values from the environment:

    \table
    \header \o Shader Variable \o Purpose
    \row \o \c qt_ModelViewProjectionMatrix
         \o Combination of the modelview and projection matrices into a
            single 4x4 matrix.
    \row \o \c qt_ModelViewMatrix
         \o Modelview matrix without the projection.  This is typically
            used for performing calculations in eye co-ordinates.
    \row \o \c qt_ProjectionMatrix
         \o Projection matrix without the modelview.
    \row \o \c qt_NormalMatrix
         \o Normal matrix, which is the transpose of the inverse of the
            top-left 3x3 part of the modelview matrix.  This is typically
            used in lighting calcuations to transform \c qt_Normal.
    \row \o \c qt_WorldMatrix
         \o Modelview matrix without the eye position and orientation
            component.  See QGLPainter::worldMatrix() for further
            information.
    \row \o \c qt_Texture0
         \o Sampler holding the texture from the Effect::texture property.
    \row \o \c qt_Color
         \o Set to the value of the Effect::color property.
    \endtable

    The above variables are usually declared in the shaders as follows
    (where \c highp may be replaced with \c mediump or \c lowp depending
    upon the shader's precision requirements):

    \code
    uniform highp mat4 qt_ModelViewProjectionMatrix;
    uniform highp mat4 qt_ModelViewMatrix;
    uniform highp mat3 qt_NormalMatrix;
    uniform sampler2D qt_Texture0;
    uniform highp vec4 qt_Color;
    \endcode

    Other lighting and material values, such as the ambient, diffuse,
    and specular colors, can be passed to the shader program using
    custom uniform variables, or the standard variable names described
    in the QGLShaderProgramEffect documentation.

    \section1 Custom uniform variables

    Many properties defined on the ShaderProgram are automatically exposed as
    uniforms for the fragment and vertex shaders under the same name.

    QML and shader types do not match exactly, so the following table shows
    how QML properties should be declared in qml compared to shader programs:

    \table
    \header \o QML Property \o Shader Program Variable
\row \o \code property double myDouble : 1.0 \endcode \o uniform highp float myDouble;
    \row \o \code property real myReal : 1.0 \endcode \o uniform mediump float myReal;
    \row \o \code property bool myBoolean : true \endcode \o uniform bool myBoolean;
    \row \o \code property int myInt : 1 \endcode \o uniform int myInt;
    \row \o \code property variant myPoint : Qt.point(1, 1) \endcode \o uniform mediump vec2 myPoint;
    \row \o \code property variant myPointF : Qt.point(1.0, 1.0) \endcode \o uniform mediump vec2 myPointF;
    \row \o \code property variant mySize : Qt.size(1.0, 1.0) \endcode \o uniform mediump vec2 mySize;
    \row \o \code property color myColor : "#80c342" \endcode \o uniform lowp vec4 myColor;
    \row \o \code property variant myMatrix3x3 :
            [1.0, 0.0, 0.0,
             0.0, 1.0, 0.0,
             0.0, 0.0, 1.0] \endcode \o uniform mat3 myMatrix3x3;
    \row \o \code property variant myMatrix4x4 :
        [1.0 , 0.0, 0.0, 0.0,
        0.0, 1.0, 0.0, 0.0,
        0.0, 0.0, 1.0, 0.0,
        0.0, 0.0, 0.0, 1.0 ]\endcode \o uniform mat4 myMatrix4x4;
    \row \o \code property string imageExample :
        "http://example.com/image.png" \endcode \o uniform sampler2D imageExample;
    \endtable

    Note: The precision hints in this table are just examples.  highp,
    mediump, and lowp do not map directly onto floats, doubles, colors etc.
    Choose the most appropriate variable type for your qml or javascript, and
    the most appropriate precision for your shader program.

    Be aware that variant properties in general and matrices in particular
    can have significant performance implications.  Conversion from variants
    can be slow, and matrices can consume multiple slots for uniforms, which
    are usually limited by hardware.

    String properties are assumed to be urls to images for use in textures.
    Where these images are remote, they are loaded in the background and bound
    to the effect when they are ready.
    \sa QGLGraphicsViewportItem
*/

class ShaderProgramEffect;
QT_BEGIN_NAMESPACE

class ShaderProgramPrivate
{
public:
    ShaderProgramPrivate()
        : regenerate(false)
        , shadersSupported(true) // Assume supported until known otherwise.
        , effect(0)
    {
    }

    QString vertexShader;
    QString fragmentShader;
    QUrl vertexShaderSource;
    QUrl fragmentShaderSource;
    bool regenerate;
    bool shadersSupported;
    ShaderProgramEffect *effect;
};


/*
  \internal
  Construction for the ShaderProgramEffect class consists of setting the key parameter values of the
  class to undefined.  As such, a shader program effect with no further initialisation will do nothing at all
  until further creation of shader programs for it has been carried out.
*/
ShaderProgramEffect::ShaderProgramEffect(ShaderProgram* parent)
{
    this->parent = parent;
    nextTextureUnit = 1;
    propertyListener = new ShaderProgramPropertyListenerEx(parent, this);
}

/*
  \internal
  Destruction entails deletion of the underlying \l QGLShaderProgram which forms the functional core of the
  class.
*/
ShaderProgramEffect::~ShaderProgramEffect()
{
    QList<QGLTexture2D*> textures = texture2Ds.values();
    QGLTexture2D* texture;
    foreach (texture, textures)
        delete texture;
}

/*
  \internal
  The act of shader programe creation can be undertakn in the manner defined for the QGLShaderProgram class.
  Failure to successfully carry out creation will result in a warning message.  Success will auto-populate the
  parameter fields of the ShaderProgramEffect with the necessary values based on the shader program.

  The vertex shader source is defined as a QString in the \a vertexShader parameter, while the fragment shader
  is provided in the \a fragmentShader parameter.
*/
bool ShaderProgramEffect::create
    (const QString& vertexShader, const QString& fragmentShader)
{
    if (!QGLShaderProgram::hasOpenGLShaderPrograms())
        return false;

    setVertexShader(vertexShader.toLatin1());
    setFragmentShader(fragmentShader.toLatin1());

    return true;
}

/*!
  \internal
  Convenience function to setup the relationship between object properties
  and shader uniforms for later use.
  */
void ShaderProgramEffect::afterLink()
{
    propertyIdsToUniformLocations.clear();
    uniformLocationsToTextureUnits.clear();
    nextTextureUnit = 1;
    propertyListener->disconnect();
    if (parent.data() == 0)
    {
        return;
    }
    QObject::connect(propertyListener, SIGNAL(propertyChanged()), parent.data(), SIGNAL(effectChanged()));

    const QMetaObject* parentMetaObject = parent.data()->metaObject();
    int parentMethodCount = parentMetaObject->methodCount();

    for (int i = parentMetaObject->propertyOffset();
    i < parentMetaObject->propertyCount(); i++)
    {
        QMetaProperty metaProperty = parentMetaObject->property(i);
        QByteArray propertyName = metaProperty.name();
        int location = program()->uniformLocation(propertyName);
        // -1 indicates that the program does not use the variable,
        // so ignore those variables.
        if (location != -1)
        {
            dirtyProperties.append(i);
            propertyIdsToUniformLocations[i] = location;
            if (metaProperty.hasNotifySignal())
            {
                QMetaMethod notifySignal = metaProperty.notifySignal();

                int signalIndex = notifySignal.methodIndex();

                // Connect the myFooChanged() signal from the ShaderProgram
                // to the corresponding imaginary slot on the listener
                // Use the method count to make sure that we don't stomp on
                // real methods and add the property index to tell the
                // properties apart.
                // Warning: Subclasses of ShaderProgramPropertyListener will
                // generate spurious property updates and lots of warnings
                // and might even crash
                QMetaObject::connect(parent.data(), signalIndex,
                                     propertyListener,  parentMethodCount + i);
            } else {
                qWarning() << "Warning: No notification signal found for property: " << propertyName;
                propertiesWithoutNotificationSignal.append(i);
            }
        }
    }

    // Refresh everything
    this->setPropertiesDirty();
}

/*!
  \internal
  Precondition: list is a list of floats
 */
static inline void setUniformFromFloatList(QGLShaderProgram *program, int uniformLocation, QList<QVariant> list)
{
    switch(list.length())
    {
    case 1:
        program->setUniformValue(uniformLocation, list.at(0).toFloat());
        break;
    case 2:
        program->setUniformValue(uniformLocation,
                                 list.at(0).toFloat(),
                                 list.at(1).toFloat());
        break;
    case 3:
        program->setUniformValue(uniformLocation,
                                 list.at(0).toFloat(),
                                 list.at(1).toFloat(),
                                 list.at(2).toFloat());
        break;
    case 4:
        program->setUniformValue(uniformLocation,
                                 list.at(0).toFloat(),
                                 list.at(1).toFloat(),
                                 list.at(2).toFloat(),
                                 list.at(3).toFloat());
        break;
    case 9:
        {
            QMatrix3x3 matrix;
            for (int i = 0; i < 9; i++)
            {
                matrix(i / 3, i % 3) = list.at(i).toFloat();
            }
            program->setUniformValue(uniformLocation, matrix);
        }
        break;
    case 16:
        {
            QMatrix4x4 matrix;
            for (int i = 0; i < 16; i++)
            {
                matrix( i / 4, i % 4) = list.at(i).toFloat();
            }
            program->setUniformValue(uniformLocation, matrix);
        }
        break;
    default:
        // Very little information available to make this warning any more helpful
        qWarning() << "Warning: unexpected list size: " << list.size() << ", only 1-4, 9 and 16 supported";
    }
}

/*!
  \internal
  This performs all updates for the shader program given a QGLPainter \a painter, and the type of update
  being carried out based on the \a updates field, which is an enumeration of the possible painter updates.
*/
void ShaderProgramEffect::update
    (QGLPainter *painter, QGLPainter::Updates updates)
{
    if (changedTextures.count() > 0)
    {
        foreach (int i, changedTextures)
        {
            if (!images.contains(i))
            {
                changedTextures.remove(i);
                continue;
            }

            if (!images[i].isNull())
            {
                setUniform(i, images[i], painter);
            } else
            {
                qWarning() << "Warning: ShaderProgramEffect failed to apply texture for uniform" << i << (urls.contains(i) ? QLatin1String(" url: ") + urls[i] : QString());
            }
            changedTextures.remove(i);
        }
    }

    // Update the standard uniform variables.
    QGLShaderProgramEffect::update(painter, updates);

    // Assign custom properties if they exist
    if (!parent.data() || !(propertyIdsToUniformLocations.count() > 0))
        return;

    // update dirty properties and remove them from the list
    int propertyIndex;
    QList<int> propertiesNotUpdated;
    foreach (propertyIndex, dirtyProperties)
    {
        if (!setUniformForPropertyIndex(propertyIndex, painter))
        {
            propertiesNotUpdated.append(propertyIndex);
        };
    }
    dirtyProperties.clear();
    dirtyProperties.append(propertiesNotUpdated);

    // always update the properties we can't track
    foreach (propertyIndex, propertiesWithoutNotificationSignal)
    {
        setUniformForPropertyIndex(propertyIndex, painter);
    }
}

inline QGLTexture2D* ShaderProgramEffect::textureForUniformValue(int uniformLocation)
{
    QGLTexture2D* result = texture2Ds.value(uniformLocation);
    if (result == 0)
    {
        result = new QGLTexture2D();
        texture2Ds[uniformLocation] = result;
    }
    return result;
}

inline bool ShaderProgramEffect::setUniformForPropertyIndex(int propertyIndex, QGLPainter *painter)
{
    QGLShaderProgram *program = this->program();
    int uniformLocation = propertyIdsToUniformLocations[propertyIndex];

    QVariant value =
            parent.data()->metaObject()->property(propertyIndex).read(parent.data());

    switch(value.type())
    {
    case QVariant::Double:
        // Convert double to float to pass to shader program
    case QMetaType::Float:
        program->setUniformValue(uniformLocation, value.toFloat());
        break;
    case QVariant::Int:
        program->setUniformValue(uniformLocation, value.toInt());
        break;
    case QVariant::UInt:
        program->setUniformValue(uniformLocation, value.toUInt());
        break;
    case QVariant::Bool:
        program->setUniformValue(uniformLocation, value.toBool());
        break;
    case QVariant::Color:
        program->setUniformValue(uniformLocation, value.value<QColor>());
        break;
    case QVariant::List:
        setUniformFromFloatList(program, uniformLocation, value.toList());
        break;
    case QVariant::Point:
        program->setUniformValue(uniformLocation, value.toPoint());
        break;
    case QVariant::PointF:
        program->setUniformValue(uniformLocation, value.toPointF());
        break;
    case QVariant::Size:
        program->setUniformValue(uniformLocation, value.toSize());
        break;
    case QVariant::SizeF:
        program->setUniformValue(uniformLocation, value.toSizeF());
        break;
    case QVariant::Matrix4x4:
        program->setUniformValue(uniformLocation, value.value<QMatrix4x4>());
        break;
    case QVariant::Vector2D:
        program->setUniformValue(uniformLocation, value.value<QVector2D>());
        break;
    case QVariant::Vector3D:
        program->setUniformValue(uniformLocation, value.value<QVector3D>());
        break;
    case QVariant::Vector4D:
        program->setUniformValue(uniformLocation, value.value<QVector4D>());
        break;
    case QVariant::String:
        {
            // We assume strings are URLs to images for textures
            QString urlString = value.toString();
            processTextureUrl(uniformLocation, urlString);
        }
        break;
    case QVariant::Image:
        {
            QImage image(value.toString());
            setUniform(uniformLocation, image, painter);
        }
        break;
    default:
        qWarning() << "Unrecognized variant for property " << parent.data()->metaObject()->property(propertyIndex).name() << " of type " << value.typeName() << ", could not set corresponding shader variable";
    }
    return true;
}

/*!
  \internal Helper function for applying a \a pixmap to a texture for a shader program.  This function should be called from within update() in order to have access to the right GL context through the \a painter.
  */
void ShaderProgramEffect::setUniform
        (int uniformLocation, const QPixmap pixmap, QGLPainter* painter)
{
    // TODO: Perspective correction
    QGLTexture2D* texture = textureForUniformValue(uniformLocation);
    int unit = textureUnitForUniformValue(uniformLocation);
    if (texture != 0)
    {
        texture->setPixmap(pixmap);
        painter->glActiveTexture(GL_TEXTURE0 + unit);
        texture->bind();
        program()->setUniformValue(uniformLocation, unit);
    }
}

/*!
  \internal Helper function for applying an \a images to a texture for a shader program.  This function should be called from within update() in order to have access to the right GL context through the \a painter.
  */
void ShaderProgramEffect::setUniform
        (int uniformLocation, const QImage& image, QGLPainter* painter)
{
    // TODO: Perspective correction
    QGLTexture2D* texture = textureForUniformValue(uniformLocation);
    int unit = textureUnitForUniformValue(uniformLocation);
    if (texture != 0)
    {
        texture->setImage(image);
        painter->glActiveTexture(GL_TEXTURE0 + unit);
        texture->bind();
        program()->setUniformValue(uniformLocation, unit);
    }
}

/*!
  \internal Find the texture unit to associate with \a uniformLocation.
*/
int ShaderProgramEffect::textureUnitForUniformValue(int uniformLocation)
{
    int unit = uniformLocationsToTextureUnits.value(uniformLocation, -1);
    if (unit == -1) {
        unit = nextTextureUnit++;
        uniformLocationsToTextureUnits[uniformLocation] = unit;
    }
    return unit;
}

/*!
  \internal set all properties dirty so they are reuploaded
  next update()
  */
void ShaderProgramEffect::setPropertiesDirty()
{
    dirtyProperties = this->propertyIdsToUniformLocations.keys();
}

/*!
  \internal Set a specific property as dirty so that it is reuploaded
  next update()
  */
void ShaderProgramEffect::setPropertyDirty(int property)
{
    if (dirtyProperties.indexOf(property) == -1)
    {
        dirtyProperties.append(property);
    }
}

/*!
  \internal Update the image for the texture bound at \a uniform location with
    the the image at \a urlString.  If \a urlString is a remote resource, this
    starts an asycnrounous loading process.

    Note: Consecutive calls with the same url for a given uniform are ignored.
*/
void ShaderProgramEffect::processTextureUrl(int uniformLocation, QString urlString)
{
    QUrl url(urlString);
    if (urlString.isEmpty() &&
       urls.contains(uniformLocation) &&
       !urls[uniformLocation].isNull())
    {
        if (images.contains(uniformLocation) && !images[uniformLocation].isNull())
        {
            images[uniformLocation] = QImage();
            urls.remove(uniformLocation);
            changedTextures.insert(uniformLocation);
            return;
        }
    };

    bool async = true;
    // Try to make path absolute:
    if (url.isRelative())
    {
        async = false;
        // Get the baseUrl from the declarative engine
        QDeclarativeContext *context =
                QDeclarativeEngine::contextForObject(parent.data());

        if (context)
        {
            QUrl baseurl = context->baseUrl();
            QUrl absolute =  baseurl.resolved(urlString);

            if (absolute.isValid())
            {
                url = absolute;
                urlString = absolute.toString();
            } else {
                qWarning() << "Warning: failed to resolve relative path " <<
                        urlString;
            }
        }
    };

    if (urlString != urls[uniformLocation])
    {
        if (url.scheme() != QLatin1String("file"))
        {
            // TODO - support network URL's for loading - note that this feature is for
            // the Qt3D 1.1 release and there is no point in implementing it until for example
            // model loading and all other parts of Qt3D support it.  Also when it is implemented
            // it has to be done with a facility that does not depend on private headers in
            // QtDeclarative which can change within minor dot-point releases.
            qWarning("Network URL's not yet supported - %s", qPrintable(urlString));
        }
        else
        {
            QString localFile = url.toLocalFile();
            if (localFile.endsWith(QLatin1String(".dds")))
            {
                qWarning("Shader effects with compressed textures not supported: %s",
                         qPrintable(urlString));
            }
            else
            {
                QImage im(localFile);
                if (im.isNull())
                {
                    qWarning("Could not load image from local file path - %s", qPrintable(localFile));
                }
                else
                {
                    images[uniformLocation] = im;
                    changedTextures.insert(uniformLocation);
                }
            }
        }
    }
}

/*!
  \internal
  Construction of the shader program and assignment of its \a parent object.
*/
ShaderProgram::ShaderProgram(QObject *parent)
    : QDeclarativeEffect(parent)
{
    d = new ShaderProgramPrivate();
}

/*!
  \internal
  Destruction of the ShaderProgram entails deletion of private data, and explicit deletion of the
  underlying ShaderProgramEffect defined by the class.
*/
ShaderProgram::~ShaderProgram()
{
    delete d->effect;
    delete d;
}

/*!
    \qmlproperty string ShaderProgram::vertexShader

    This property defines the source for the vertex shader to be implemented by this
    instance of the ShaderProgram.  This property and the vertexShaderSource()
    property both effect the same underlying object, so setting one will override
    the other.

  \sa fragmentShader, vertexShaderSource
*/
QString ShaderProgram::vertexShader() const
{
    return d->vertexShader;
}

void ShaderProgram::setVertexShader(const QString& value)
{
    if (!d->vertexShaderSource.isEmpty() || value != d->vertexShader)
    {
        d->vertexShader = value;
        d->regenerate = true;
        d->vertexShaderSource = QUrl();
        emit shaderChanged();
        emit effectChanged();
    }
}

/*!
    \qmlproperty string ShaderProgram::fragmentShader
    This property defines the source for the fragment shader (ie. pixel shader) to be
    implemented by this instance of the ShaderProgram.  This property and the
    fragmentShaderSource() property both effect the same underlying object, so
    setting one will override the other.

  \sa vertexShader, fragmentShaderSource
*/
QString ShaderProgram::fragmentShader() const
{
    return d->fragmentShader;
}

void ShaderProgram::setFragmentShader(const QString& value)
{
    if (!d->fragmentShaderSource.isEmpty() || value != d->fragmentShader)
    {
        d->fragmentShader = value;
        d->regenerate = true;
        d->fragmentShaderSource = QUrl();
        emit shaderChanged();
        emit effectChanged();
    }
}

/*!
    \qmlproperty QUrl ShaderProgram::vertexShaderSource
    This property allows the source for the vertex shader to be set to the contents
    of a file containing shader source code.  This property and the vertexShader()
    property both effect the same underlying object, so setting one will override
    the other.

    Note that at present networked URLs are not supported, only local files.  If a
    URL has not been set for the vertex shader, for example because it was
    specified via the vertexShader() in-line shader code property, then this property
    will return a null (empty) QUrl.

    \sa vertexShader, fragmentShaderSource
*/
QUrl ShaderProgram::vertexShaderSource() const
{
    return d->vertexShaderSource;
}

void ShaderProgram::setVertexShaderSource(const QUrl &url)
{
    if (!url.isEmpty() && url.isValid() && url != d->vertexShaderSource)
    {
        if (url.scheme() == QLatin1String("file"))
        {
            QString fn = url.toLocalFile();
            QFile vs(fn);
            if (vs.open(QIODevice::ReadOnly))
            {
                d->vertexShader = vs.readAll();
                d->vertexShaderSource = url;
                emit shaderChanged();
                emit effectChanged();
                d->regenerate = true;
            }
            else
            {
                qWarning() << "Unable to read" << url;
            }
        }
        else
        {
            qWarning() << "vertexShaderSource property does not (yet) support non-file URLs";
        }
    }
}

/*!
    \qmlproperty QUrl ShaderProgram::fragmentShaderSource
    This property allows the source for the fragment shader to be set to the contents
    of a file containing shader source code.  This property and the vertexShader()
    property both effect the same underlying object, so setting one will override
    the other.

    Note that at present networked URLs are not supported, only local files.  If a
    URL has not been set for the fragment shader, for example because it was
    specified via the fragmentShader() in-line shader code property, then this property
    will return a null (empty) QUrl.

    \sa fragmentShader, vertexShaderSource
*/
QUrl ShaderProgram::fragmentShaderSource() const
{
    return d->fragmentShaderSource;
}

void ShaderProgram::setFragmentShaderSource(const QUrl &url)
{
    if (!url.isEmpty() && url.isValid() && url != d->fragmentShaderSource)
    {
        if (url.scheme() == QLatin1String("file"))
        {
            QString fn = url.toLocalFile();
            QFile fs(fn);
            if (fs.open(QIODevice::ReadOnly))
            {
                d->fragmentShader = fs.readAll();
                d->fragmentShaderSource = url;
                emit shaderChanged();
                emit effectChanged();
                d->regenerate = true;
            }
            else
            {
                qWarning() << "Unable to read fragment shader" << url;
            }
        }
        else
        {
            qWarning() << "fragmentShaderSource property does not (yet) support non-file URLs";
        }
    }
}

/*!
  \internal
  Enables the effect for a given \a painter.  If the effect has not been created yet, this function will
  attempt to do so.
*/
void ShaderProgram::enableEffect(QGLPainter *painter)
{
    if (!d->shadersSupported && !d->regenerate) {
        // Use a simple fallback effect.
        QDeclarativeEffect::enableEffect(painter);
        return;
    }
    if (!d->effect) {
        // note that the ShaderProgramEffect can also be created when this
        // effect is applied to a QGLSceneNode if that happens first
        d->effect = new ShaderProgramEffect(this);
        if (!d->effect->create(d->vertexShader, d->fragmentShader)) {
            delete d->effect;
            d->effect = 0;
            QDeclarativeEffect::enableEffect(painter);
            d->regenerate = false;
            d->shadersSupported = false;
            return;
        }
        d->shadersSupported = true;
    } else if (d->regenerate) {
        if (!d->effect->create(d->vertexShader, d->fragmentShader)) {
            delete d->effect;
            d->effect = 0;
            QDeclarativeEffect::enableEffect(painter);
            d->regenerate = false;
            d->shadersSupported = false;
            return;
        }
        d->shadersSupported = true;
    }
    d->regenerate = false;
    painter->setUserEffect(d->effect);
    painter->setColor(color());
    QGLTexture2D *tex = texture2D();
    painter->glActiveTexture(GL_TEXTURE0);
    if (tex)
        tex->bind();
    else
        glBindTexture(GL_TEXTURE_2D, 0);
}

/*!
  \internal
  Set a scenenode's material and effect properties to enact this effect.

  This can happen before glInitialize, so setup is delayed until the effect is
  used or explicitly initialized.
*/
void ShaderProgram::applyTo(QGLSceneNode *node)
{
    if (!d->effect) {
        // This function is often called during setup, before glInitilization,
        // so create the effect now, and then initializion it later.
        d->effect = new ShaderProgramEffect(this);
        d->regenerate = true;
    }
    node->setUserEffect(d->effect);
}

/*!
  \internal
  Mark all properties as dirty to be re-uploaded in the next update
*/
void ShaderProgram::markAllPropertiesDirty()
{
    d->effect->setPropertiesDirty();
}

/*!
  \internal
  Mark a \a property as dirty to be re-uploaded in the next update
  */
void ShaderProgram::markPropertyDirty(int property)
{
    d->effect->setPropertyDirty(property);
}

/*!
  \qmlsignal ShaderProgram::onFinishedLoading()
  Emitted when the last remote resource request is resolved, and implies that
  the effect is ready to be displayed.
*/

/*!
    \internal
    A subclass without the Q_OBJECT macro in order to use the qt_metacall trick to track property changes.

    It is also conveniently placed to connect appropriate properties to
    Effect::effectChanged() to trigger timely updates.
  */
ShaderProgramPropertyListenerEx::ShaderProgramPropertyListenerEx(ShaderProgram *parent, ShaderProgramEffect* effect)
    : ShaderProgramPropertyListener(parent), effect(effect)
{
    shaderProgramMethodCount = parent->metaObject()->methodCount();
}

/*!
    \internal
*/
ShaderProgramPropertyListenerEx::~ShaderProgramPropertyListenerEx()
{
}

/*!
    \internal
    Find calls to the "imaginary" slots, and mark the appropriate property
    as dirty.
*/
int ShaderProgramPropertyListenerEx::qt_metacall(QMetaObject::Call c, int id, void **a)
{
    if (c == QMetaObject::InvokeMetaMethod )
    {
        if (id >= shaderProgramMethodCount) {
            effect->setPropertyDirty(id - shaderProgramMethodCount);
            emit propertyChanged();
        }
        // Consume the metacall
        return -1;
    }

    return ShaderProgramPropertyListener::qt_metacall(c, id, a);
}

QT_END_NAMESPACE